# Tag Info

### Intuition for the time/energy connection?

Seem the answer of mine is quite a late one for the Asker @TEH. For coming freshman in Physics Exchange, I offer a metaphor associated with the intuition of the "time/energy conservation law"...
1 vote
Accepted

### Questions related to conservation of momentum

Since the mass is thrown out with a sideways velocity relative to the car, it still has a velocity $v$ in the direction of the car immediately after the throw. This means that the momentum ...
Accepted

### How is it that underground nuclear tests create huge caverns without violating conservation of mass?

When the bomb goes off underground, the surrounding rock gets fractured and the fireball pushes the rock away in all directions. That rock mass does not disappear; it is displaced through a ...

### Questions related to conservation of momentum

considering the given answer, it might meant that before throwing the mass the velocity in x(assumed) direction was 0 and after throwing it will remain 0 which means it has not changed. however, if we ...

### What referential should I use? Ping pong and water cup

Since the experiment can replace the water by sand or by a poorly bouncing heavier ball I think the approach with Archimedes law does not work better than the explanations in the other link.

### Where does this conservation of momentum gedankenexperiment go wrong?

As an addendum to the other comments, which generally do a good job of making the mathematical case that the block hasn't done 1J of work on you, I would like to add my personal visualization of the ...

### Where does this conservation of momentum gedankenexperiment go wrong?

Start with two bodies [A][B] in contact. [A] has a mass of 100 kg, [B] has a mass of 1 kg. They apply a 1 N force on each other. 1 fraction of a second later, they are not in contact. They are no ...

### How does the Hong-Ou-Mandel (HOM) effect conserve photon momentum?

The only easy way to see generic momentum conservation in quantum experiments is to not look at just one possible outcome, but rather to look at expectation values (weighted averages, over all ...

### Why, when deriving the Einstein equations, do we want the energy-momentum tensor to be divergence free?

When expressed in terms of the stress tensor density $$𝔗^μ_ν = \sqrt{|g|} g^{μρ} T_{ρν},$$ rather than the stress tensor $T_{ρν}$, ifself, the continuity equation is just a transport law, such as you ...
Accepted

### Necessity and Sufficiency of Yang-Baxter Equation for Integrability

This is a hard question, and is closely related to what you precisely mean by (quantum) integrability. The definition that you use is sometimes called Yang-Baxter integrability: those models for which ...
1 vote

### Is colour the conserved charge of global $SU(3)$ color symmetry?

For a classical gauge charge, there is a charge component $\left(e_a: a = 0,1,⋯,N-1\right)$ for each of the $N$ dimensions of the gauge group. For $SU(3)$, $N = 8$. The charge precesses under Wong's ...
1 vote
Accepted

### Is colour the conserved charge of global $SU(3)$ color symmetry?

There is no contradiction in the three answers you are citing, just loose language. Only the third answer deals with your spare globally symmetric Lagrangian. The other two deal with QCD, its gauged (...

### Equation in Noether's paper

Divergences here mean terms of the form $$\sum_{\mu=1}^n\frac{\partial F^{\mu}(x,\phi(x), \ldots)}{\partial x^{\mu}}.$$ The equation is a consequence of applying Leibniz rule (multiple times). Under ...

### Proof that if the 3-momentum is conserved then so is energy. (Weinberg's Gravitation and Cosmology)

Let $p^a = mu^a$ be the 4-momentum of a single particle with 4-velocity $u^a$. Also, w.r.t. to another frame (denoted by prime) $${p'}^a = {\Lambda^a}_{b} p^b \,.$$ For a ensemble of $n$ particles ...

### Conserved Quantities in Kepler Problem?

He could (and should) count the mechanical energy as a conserved quantity. He also didn't mention that the total momentum of the 2 objects is 3 integrals of motion. However, not all quantities are ...